Method of inhibiting neurotrophin-receptor binding

ABSTRACT

The present invention relates to compositions which inhibit the binding of nerve growth factor to the p75 NTR  common neurotrophin receptor and methods of use thereof. In one embodiment, the compound which inhibits binding of nerve growth factor to p75 NTR  comprises, particularly when bound to nerve growth factor, at least two of the following: (1) a first electronegative atom or functional group positioned to interact with Lys 34  of nerve growth factor; (2) a second electronegative atom or functional group positioned to interact with Lys 95  of nerve growth factor; (3) a third electronegative atom or functional group positioned to interact with Lys 88  of nerve growth factor; (4) a fourth electronegative atom or functional group positioned to interact with Lys 32  of nerve growth factor; and (5) a hydrophobic moiety which interacts with the hydrophobic region formed by Ile 31 , Phe 101  and Phe 86  of nerve growth factor.

RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No. 09/562,721, filed May 2, 2000 now U.S. Pat. No. 6,468,990, which claims the benefit under 35 U.S.C. §119(e) to U.S. provisional patent application 60/134,578, filed May 17, 1999, the contents of each of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The neurotrophins are a family of structurally and functionally related proteins, including Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF), Neurotrophin-3 (NT-3), Neurotrophin-4/5 (NT-4/5) and Neurotrophin-6 (NT-6). These proteins promote the survival and differentiation of diverse neuronal populations in both the peripheral and central nervous systems (Hefti, 1986; Hefti and Weiner, 1986; Levi-Montalcini, 1987; Barde, 1989; Leibrock et al., 1989; Maisonpierre et al., 1990; Rosenthal et al., 1990; Hohn et al., 1990; Gotz et al., 1994; Maness et al., 1994) and are involved in the pathogenesis of diverse neurological disorders. Neurotrophins exert many of their biological effects through specific interactions with a class of transmembrane receptor tyrosine kinases (trkA, trkB and trkC) (Kaplan et al., 1991; Klein et al., 1991, 1992; Soppet et al., 1991; Squinto et al., 1991; Berkemeier et al., 1991; Escandon et al., 1993; Lamballe et al., 1991). Specificity of neurotrophin action results from their selective interactions with the trk receptors. That is, trkA only binds NGF (Kaplan et al., 1991; Klein et al., 1991); trkB binds BDNF and NT-4/5 (Soppet et al., 1991; Squinto et al., 1991; Berkemeier et al., 1991; Escandon et al., 1993; Lamballe et al., 1991; Klein et al., 1992; Vale and Shooter, 1985; Barbacid, 1993); and trkC exclusively binds NT-3 (Lamballe et al., 1991; Vale and Shooter, 1985). This is particularly evident when the trk receptors are coexpressed with the common neurotrophin receptor p75^(NTR). (For review see Meakin and Shooter, 1992; Barbacid, 1993; Chao, 1994; Bradshaw et al., 1994; Ibáñez, 1995).

The common neurotrophin receptor p75^(NTR) is a transmembrane glycoprotein structurally related to the tumor necrosis factor and CD-40 receptors (Meakin and Shooter, 1992; Rydén and Ibáñez, 1996). As all neurotrophins bind to p75^(NTR) with similar affinity (Rodriguez-Tébar et al., 1990; Hallböök et al., 1991; Rodriguez-Tébar et al., 1992; Ibáñez, 1995), neurotrophin specificity is conventionally thought to be caused by the binding selectivity for trk receptors which are differentially expressed in different neuronal populations (Ibáñez, 1995). However, accumulated experimental data on neurotrophin activity reveal important functional aspects of p75^(NTR) (Heldin et al., 1989; Jing et al., 1992; Herrmann, 1993; Barker and Shooter, 1994; Dobrowsky et al., 1994, Matsumoto et al., 1995; Marchetti et al., 1996; Washiyama et al., 1996). The common neurotrophin receptor enhances functions and increases binding specificity of trk receptors (Barker and Shooter, 1994; Mahadeo et al., 1994; Chao and Hempstead, 1995; Rydén and Ibáñez, 1996). In addition, p75^(NTR) possesses unique, trk-independent signaling properties which involve ceramide production through activation of the sphingomyelin cycle (Dobrowsky et al., 1994), apoptosis (cell death) (Van der Zee et al., 1996; Cassacia-Bonnefil et al., 1996; Frade et al., 1996), and activation of the transcription factor NFκB (Carter et al., 1996). Recently, p75^(NTR) has been demonstrated to participate in human melanoma progression (Herrmann et al., 1993; Marchetti et al., 1996). Furthermore, NGF and NT-3 increase the production of heparin by 70 W melanoma cells, which is associated with their metastatic potential (Marchetti et al., 1996). Although this effect has been shown to be mediated by the common neurotrophin receptor, neither BDNF nor NT-4/5 appeared to be active.

Due to the implication of NGF/p75^(NTR) binding in various disease states, a need exists for pharmaceutical agents and methods of use thereof for interfering with the binding of NGF to the p75^(NTR) common neurotrophin receptor.

SUMMARY OF THE INVENTION

The present invention relates to the discovery of molecular structural features which contribute to the ability of a compound to inhibit the binding of NGF to the common neurotrophin receptor p75^(NTR). Compounds which have these features are of use, for example, for inhibiting binding of NGF to p75^(NTR). Such compounds can also be used to treat a patient having a condition which is mediated, at least in part, by the binding of NGF to p₇₅ ^(NTR).

In one embodiment, the present invention relates to compositions which inhibit the binding of nerve growth factor to the p75NTR common neurotrophin receptor and methods of use thereof.

In one embodiment, the compound which inhibits binding of nerve growth factor to p75^(NTR) comprises at least two of the following: (1) a first electronegative atom or functional group positioned to interact with Lys³⁴ of nerve growth factor; (2) a second electronegative atom or functional group positioned to interact with Lys⁹⁵ of nerve growth factor; (3) a third electronegative atom or functional group positioned to interact with Lys⁸⁸ of nerve growth factor; (4) a fourth electronegative atom or functional group positioned to interact with Lys³² of nerve growth factor; and (5) a hydrophobic moiety which interacts with the hydrophobic region formed by amino acid residues of nerve growth factor, including Ile³¹, Phe¹⁰¹ and Phe⁸⁶. Such inhibitors, preferably, bind nerve growth factor via at least two of the foregoing interactions.

In one embodiment, compounds which inhibit binding of nerve growth factor to p75^(NTR) have Formula 1,

In Formula 1, D₁, D₂, E₁, E₂ and G are each, independently, an sp²-hybridized carbon or nitrogen atom. One of X₁ and X₂ is a hydrogen atom or absent, while the other is an electronegative atom or an electronegative functional group. R and R₂ are each, independently, an electronegative atom or an electronegative functional group, such as O, S, CH₂, or NR₃, where R₃ is H, allyl, preferably C₁–C₆-alkyl, or aryl, such as phenyl. R, R₂ and one of X₁ and X₂ can also each be, independently, an electronegative atom or functional group, such as alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl group or a fluorine, chlorine, bromine or iodine atom. Y is N, O, S, C-L or N-L, where L is H, alkyl, preferably C₁–C₆-alkyl, or an electronegative atom or functional group, such as, but not limited to, alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl groups or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. Z and Z₁ are each, independently, O, S, CH, C(O), N, NH, N-alkyl, N-cycloalkyl and N-P, where P is a carbohydrate moiety, such as a monosaccharide group, for example, a fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl or lyxosyl group. T₁ and T₂ are each, independently, an sp²- or sp³-hybridized carbon or nitrogen atom. a, b, and c are each 0 or 1, provided that at least one of b and c is 1. R₁ is a monocyclic or polycyclic aryl or heteroaryl, monosaccharide or oligosaccharide, alkyl, cycloalkyl, arylalkyl, alkylamino or alkoxy group which is substituted with at least one substituent selected from the group consisting of electronegative atoms and electronegative functional groups.

It will be appreciated that in this and the following structures, the lines connecting the variables can be single or double bonds. In addition, hydrogen atoms are added to the variables as necessary to complete the valence of the atom.

In another embodiment, the NGF/p75^(NTR) binding inhibitor has Formula 3

where D₁, D₂, X₁, X₂, Y, E₁, E₂, T₁, T₂, R, G, R₁, R₂, and c have the meanings given above for these variables in Formula 1. Y₁, Y₂, and Y₃ are independently selected from the identities given for Y in Formula 1. E₃ and E₄ are each, independently, an sp²-hybridized carbon or nitrogen atom, and d and h are, independently, 0 or 1.

In another embodiment, compounds which inhibit the binding of nerve growth facor to p75^(NTR) have Formula 2,

In Formula 2, D₁, D₂, E₁, E₂, E₃, E₄ and G are each, independently, an sp²-hybridized carbon or nitrogen atom. One of X₁ and X₂ is a hydrogen atom or absent, while the other is an electronegative atom or an electronegative functional group. R, R₂ and R₄ are each, independently, an electronegative atom or an electronegative functional group, such as O, S, CH₂, or NR₃, where R₃ is H, OH, alkyl, preferably C₁–C₆-allyl, or aryl, such as phenyl. R, R₂ and one of X₁ and X₂ can also each be, independently, an electronegative atom or functional group, such as alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl group or a fluorine, chlorine, bromine or iodine atom. Y is N, O, S, C-L or N-L, where L is H, alkyl, preferably C₁–C₆-alkyl, or an electronegative atom or functional group, such as, but not limited to, alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl groups or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. Z and Z₁ are each, independently, O, S, CH, C(O), N, NH, N-alkyl, N-cycloalkyl and N-P, where P is a carbohydrate moiety, such as a monosaccharide group, for example, a fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl or lyxosyl group. T₁, T₂ and T₃ are each, independently, an sp²- or sp³-hybridized carbon or nitrogen atom. When f is 0, T₃ can further have the meanings given for Z and Z₁, above. a, b, c, d, e, f, g, h and i are each 0 or 1, provided that at least one of b and c is 1, at least one of d and e is 1 and at least one of f and i is 1. R₁ is a monocyclic or polycyclic aryl or heteroaryl, monosaccharide or oligosaccharide, alkyl, cycloalkyl, arylalkyl, alkylamine or alkoxy group which is substituted with at least one substituent selected from the group consisting of electronegative atoms and electronegative functional groups.

In another embodiment, a compound which inhibits the binding of NGF to p75^(NTR) has Formula 5,

wherein D₁, D₂, X₁, X₂, E₁, E₂, E₃, T₁, T₂, T₃, Z, G, R, R₁, R₂, R₄, b, e, f, i, and c have the meanings given for these variables in Formula 2. Y₁, Y₂, and Y₃ are independently selected from the identities given for Y in Formula 2, and h is 0 or 1. E₅ and E₆ are each, independently, an sp²-hybridized carbon or nitrogen atom, and g is 0 or 1. Ring 4 can be further unsubstituted or substituted with one or more substituents, such as alkyl or aryl groups.

In another embodiment, the invention provides a pharmaceutical composition comprising at least one compound of the invention, or pharmaceutically acceptable salt thereof, in combination with a pharmaceutically acceptable carrier or excipient.

The invention also provides a method of inhibiting the binding of nerve growth factor to the p75^(NTR) receptor. The method comprises contacting cells which express the p75^(NTR) receptor with a nerve growth factor/p75^(NTR) binding inhibitor of the invention in an amount which is sufficient to inhibit binding of nerve growth factor to the p75^(NTR) receptor. The method can be practiced in vivo or in vitro.

In another embodiment, the invention relates to a method of treating a condition in a patient which is mediated by the binding of nerve growth factor to the p75^(NTR) receptor. The method comprises administering to the patient a therapeutically effective amount of a nerve growth factor/p75^(NTR) binding inhibitor of the invention. Preferably, the compound to be administered selectively inhibits the binding of nerve growth factor to p75^(NTR) in cells which do not express the NGF receptor trkA.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates examples of suitable configurations for electronegative atoms in the NGF/p75^(NTR) binding inhibitors of the invention.

FIG. 2 illustrates examples of electronegative functional groups.

FIG. 3 sets forth a synthetic pathway for certain compounds of the invention; Pg=protecting group.

FIG. 4 sets forth a synthetic pathway for certain compounds of the invention.

FIG. 5 sets forth a synthetic pathway for certain compounds of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Nerve growth factor (also referred to hereinafter as “NGF”) is a neurotrophin implicated in the pathogenesis of Alzheimer's disease, epilepsy and pain (Ben and Represa, 1990; McKee et al., 1991; Leven and Mendel, 1993; Woolf and Doubell, 1994; Rashid et al., 1995; McMahon et al., 1995). The binding of NGF to its receptors is determined by distinct sequences within its primary amino acid structure. While several regions of NGF participate in the NGF/trkA interaction, mutation studies suggest that relatively few key residues, namely those located in the NGF amino and carboxyl termini, are required for high affinity binding.

NGF displays high and low affinity binding sites in sensory and sympathetic neurons and in pheochromocytoma PC12 cells (Sutter et al., 1979; Landreth and Shooter, 1980; Schechter and Bothwell, 1981). The coexpression of the common neurotrophin p75^(NTR) receptor with trkA is required to form the high affinity binding site (Hempstead et al., 1991; Barker and Shooter, 1994; Mahadeo et al., 1994; Chao and Hempstead, 1995). Several models of the trkA-p75^(NTR) interaction have been proposed to explain high affinity NGF binding (Bothwell, 1991; Chao, 1992b; Chao and Hempstead, 1995; Wolf et al., 1995; Ross et al., 1996; Ross et al., 1997). These models differ with respect to direct (conformational model) or indirect (ligand-presentation model) interaction of p75^(NTR) with trkA. Direct trkA-p75^(NTR) interaction is consistent with much of the existing experimental data.

The hairpin loop at residues 29–35 of NGF is responsible for recognition by p75^(NTR) (Ibáñez et al., 1992; Radziejewski et al., 1992), while the amino and carboxyl termini are important binding determinants for recognition by the trkA receptor (Shih et al., 1994; Moore and Shooter, 1975; Suter et al., 1992; Burton et al., 1992; Kahle et al., 1992; Luo and Neet, 1992; Drinkwater et al., 1993; Treanor et al., 1995; Taylor et al., 1991; Shamovsky et al., 1998; Shamovsky et al., 1999; WO 98/06048). Truncation of either the amino or carboxyl terminus of NGF produces less active NGF analogues; similarly most deletion or point mutations of the amino terminus also lead to NGF analogues with diminished activity (Shih et a., 1994; Burton et al., 1992, 1995; Kahle et al., 1992; Drinkwater et al., 1993; Treanor et al., 1995; Taylor et al., 1991). On the other hand, the NGFΔ2–8 (NGF with residues 2–8 removed) and NGFΔ3–9 deletion mutants are almost as active as wild type NGF (Drinkwater et al., 1993). These NGF structure-activity relationships in combination with the considerable species variability (mouse, human, guinea pig and snake) of the amino acid sequence of the NGF termini (McDonald et al., 1991) are of potential value in understanding the NGF/trkA interaction.

NGF exerts its biological activity as a non-covalent dimer (Treanor et al., 1995; Burton et al., 1995; McDonald et al., 1991; Ibáñez et al., 1993; Bothwell and Shooter, 1977). Two 118 residue NGF monomers are dimerized by hydrophobic and van der Waals interactions between their three anti-parallel pairs of β-strands; consequently, the amino terminus of one NGF monomer and the carboxyl terminus of the other are spatially juxtaposed (McDonald et al., 1991). Furthermore, although a dimer has 2 pairs of termini, only one pair of termini is required for trkA receptor recognition (Treanor et al., 1995; Burton et al., 1995).

The X-ray crystallographic 3-dimensional structure of a dimeric mouse NGF (mNGF) has been reported (McDonald et al., 1991). However, within this structure, the amino terminus (residues 1–11) and the carboxyl terminus (residues 112–118) remain unresolved for both pairs of termini. High flexibility of the NGF termini makes it difficult to experimentally determine their bioactive conformations, particularly since transition metal ions commonly used in X-ray crystallography (McDonald et al., 1991) have high affinity for His residues (Gregory et al., 1993) which are present in the NGF amino terminus (Bradshaw et al., 1994). Indeed, conformational alterations in the receptor binding domains of NGF caused by Zn²⁺ cations leading to its inactivation have been described recently (Ross et al., 1997). Since the amino and carboxyl termini are crucial for NGF bioactivity as mediated via trkA and because of the significance of NGF in multiple neurologic disease processes, the determination of the biologically active conformation of these termini is an important and challenging problem for computational chemistry.

The present invention relates to the discovery of molecular structural features which contribute to the ability of a compound to inhibit the binding of NGF to the common neurotrophin receptor p75^(NTR). Compounds which have these features are of use, for example, for inhibiting binding of NGF to p75^(NTR). Such compounds can also be used to treat a patient having a condition which is mediated, at least in part, by the binding of NGF to p75^(NTR).

Certain compounds which inhibit the binding of NGF to p75^(NTR) are disclosed in copending U.S. patent application Ser. No. 09/292,450, incorporated herein by reference in its entirety.

In one embodiment, the present invention provides compounds which inhibit the binding of nerve growth factor (NGF) to the p75^(NTR) receptor. The compounds have at least two of the following characteristics: (1) a first electronegative atom or functional group positioned to interact with Lys³⁴ of NGF; (2) a second electronegative atom or functional group positioned to interact with Lys⁹⁵ of NGF; (3) a third electronegative atom positioned to interact with Lys⁸⁸ of NGF; (4) a fourth electronegative atom or functional group positioned to interact with Lys³² of NGF; and (5) a hydrophobic moiety which interacts with the hydrophobic region formed by Ile³¹, Phe¹⁰¹ and Phe⁸⁶ of NGF. A compound having two or more of these structural attributes is referred to herein as an “NGF/p75^(NTR) binding inhibitor”. Preferably, the NGF/p75^(NTR) binding inhibitor has at least three of the foregoing attributes when bound to NGF, more preferably at least four such attributes. Most preferably, the NGF/p75^(NTR) binding inhibitor has each of the five foregoing attributes. Typically, an NGF/p75^(NTR) binding inhibitor of the invention interacts with NGF via at least two of the foregoing interactions when bound to NGF.

The term “electronegative atom”, as used herein, refers to an atom which carries a partial or full negative charge in a particular compound under physiological conditions. The electronegative atom can be, for example, an oxygen atom, a nitrogen atom, a sulfur atom or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. Preferably the electronegative atom is an oxygen atom. The term “electronegative functional group”, as used herein, refers to a functional group which includes at least one electronegative atom. Electronegative groups include acid functional groups and other polar functional groups. For example, suitable electronegative functional groups include, but are not limited to, carbonyl, thiocarbonyl, ester, imino, amido, carboxylic acid, sulfonic acid, sulfinic acid, sulfamic acid, phosphonic acid, boronic acid, sulfate ester, hydroxyl, mercapto, cyano, cyanate, thiocyanate, isocyanate, isothiocyanate, carbonate, nitrate and nitro groups. It is to be understood that, unless otherwise indicated, reference herein to an acidic functional group also encompasses salts of that functional group in combination with a suitable cation.

An electronegative atom of the NGF/p75^(NTR) binding inhibitor bears a full or partial negative charge under physiological conditions and can, therefore, interact electrostatically with the positively charged side chain of an NGF lysine residue. This will be an interaction, such as, for example, a hydrogen bond, an ion/ion interaction, an ion/dipole interaction or a dipole/dipole interaction. The hydrophobic region or moiety of the NGF/p75^(NTR) binding inhibitor can interact with a hydrophobic region of NGF via a hydrophobic interaction. Without being bound by theory, it is believed that compounds having the disclosed structural features can interact with NGF in such a way as to interfere with, and thereby inhibit, the binding of NGF to p75^(NTR).

The ability of a compound to interact with the amino acid residues of NGF specified above can be determined using a structural model of NGF obtained using a energy-minimization algorithm, as described in published PCT application WO 98/06048, incorporated herein by reference in its entirety. For example, a molecule will interact with the specified residues of NGF, as discussed above, if it has at least 3 electronegative atoms (A, B and C) such that at least one of the following two conditions is satisfied: (i) atoms A and B are separated by 5–7 covalent bonds, B and C are separated by 6–8 covalent bonds, and A and C are separated by 10–14 covalent bonds and (ii) distance between A and B is between 4.5 and 7.5 angstroms, and distance between B and C is between 4.5 and 7.5 angstroms. See FIG. 1. The number of covalent bonds separating atoms can be determined from the structural formula of a molecule. Distance between atoms can be determined experimentally (e.g., by X-ray crystallography or NMR spectroscopy) or evaluated theoretically using any molecular builder (e.g., SYBYL from Tripos Inc. (St. Louis, Mo., USA) or QUANTA from Molecular Simulations Inc.(San Diego, Calif., USA) as well as any molecular modeling technique (e.g., AMBER from Oxford Molecular Group Inc./University of California, San Francisco or CHARMm from Molecular Simulations Inc.) or quantum chemical technique (e.g., MNDO from Oxford Molecular Group Inc. (Campbell, Calif., USA)/University of Zurich; AMPAC from Semichem (Kansas City, Mo., USA); CADPAC from Oxford Molecular Group Inc./Cambridge University; Gaussian-98 from Gaussian Inc. (Carnegie, Pa., USA); or GAMESS from Iowa State University). Examples of suitable configurations of groups A, B and C are illustrated in FIG. 1, while a representative group of electronegative functional groups is shown in FIG. 2.

Preferred NGF/p75^(NTR) inhibitors of the invention comprise a molecular scaffold or framework, to which the electronegative atoms or functional groups are attached, either directly or via an intervening moiety. The scaffold can be, for example, a cyclic or polycyclic moiety, such as a monocyclic, bicyclic or tricyclic moiety, and can include one or more hydrocarbyl or heterocyclic rings. Preferably, the scaffold includes two or more fused, planar, five- or six-membered rings. The molecular scaffold presents the attached electronegative atoms, electronegative functional groups or a combination thereof, in the proper configuration or orientation for interaction with the appropriate residues of NGF. In addition, the molecular scaffold, such as polycyclic system, or a portion thereof, can serve as the hydrophobic group which interacts with hydrophobic residues of NGF, as described above.

In one embodiment, the NGF/p75^(NTR) inhibitor is of general Formula 1,

In Formula 1, D₁, D₂, E₁, E₂ and G are each, independently, an sp²-hybridized carbon or nitrogen atom. One of X₁ and X₂ is a hydrogen atom or absent, while the other is an electronegative atom or an electronegative functional group. R and R₂ are each, independently, an electronegative atom or an electronegative functional group, such as O, S, CH₂, or NR₃, where R₃ is H, alkyl, preferably C₁–C₆-alkyl, or aryl, such as phenyl. R, R₂ and one of X₁ and X₂ can also each be, independently, an electronegative atom or functional group, such as alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl group or a fluorine, chlorine, bromine or iodine atom. Y is N, O, S, C-L or N-L, where L is H, alkyl, preferably C₁–C₆-alkyl, or an electronegative atom or functional group, such as, but not limited to, alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl groups or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. Z and Z₁ are each, independently, O, S, CH, C(O), N, NH, N-alkyl, N-cycloalkyl and N-P, where P is a carbohydrate moiety, such as a monosaccharide group, for example, a fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl or lyxosyl group. T₁ and T₂ are each, independently, an sp²- or sp³-hybridized carbon or nitrogen atom. a, b and c are each 0 or 1, provided that at least one of b and c is 1.

R₁ is a monocyclic or polycyclic aryl or heteroaryl, mono- or oligosaccharide, alkyl, cycloalkyl, arylalkyl, alkylamino or alkoxy group which is substituted with at least one substituent selected from the group consisting of electronegative atoms and electronegative functional groups. Preferred monosaccharide groups include fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl and lyxosyl groups. The electronegative substituent can be bonded to the aryl or heteroaryl ring system, alkyl, cycloalkyl, or oligo- or monosaccharide group either directly or indirectly via a bridging group, for example, an alkylene group such as a C₁–C₄-alkylene group or an oxaalkylene group. Suitable directly bonded and alkylene bridged electronegative atoms and functional groups include, but are not limited to, alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H; —OC(O)(OH); carboxyalkyl, nitroalkyl, N,N-dialkylaminosulfonyl, aminocarbonyl, alkoxycarbonyl, alkoxycarbonylalkyl, cyanocarbonylalkyl, haloalkyl, such as fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl or trichloromethyl; alkyamido or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. In one embodiment, R₁ is selected from the group consisting of groups including, but not limited to, —(CH₂)_(a)COOH; —(CH₂)_(a)NO₂; —(CH₂)_(a)OH; —(CH₂)_(a)PO₃H₂; —(CH₂)_(a)SO₃H; —(CH₂)_(a)SO₂H; —R₄(CH₂)_(a)COOH; —R₄(CH₂)_(a)NO₂; —R₄(CH₂)_(a)PO₃H₂; —R₄(CH₂)_(a)SO₂H; —R₄(CH₂)_(a)SO₃H; and —R₄(CH₂)_(a)OH, where a is 1 to 12, preferably 1 to about 4, and R₄ is NH or O.

Rings 1 and 2 are each, independently, a five- or six-membered ring and, preferably, are both planar.

It is to be understood that compounds of Formula 1 and Formulas 2, 3 and 5, below, will further include double bonds between adjacent atoms as required to satisfy the valence of each atom. That is, double bonds are added to provide the following number of total bonds to each of the following types of atoms: carbon: four bonds; nitrogen: 3 bonds; oxygen: two bonds; and sulfur: two bonds.

The term “alkyl”, as used herein, refers to a normal, branched or cyclic aliphatic hydrocarbyl group, which can be saturated or partially unsaturated. Preferred alkyl groups are normal, branched and cyclic C₁–C₈-alkyl and -alkenyl groups.

In another embodiment, the NGF/p75^(NTR) binding inhibitor of Formula 3

where D₁, D₂, X₁, X₂, Y, E₁, E₂, T₁, T₂, R, G, R₁, R₂, and c have the meanings given above for these variables in Formula 1. Y₁, Y₂, and Y₃ are independently selected from the identities given for Y in Formula 1. E₃ and E₄ are each, independently, an sp²-hybridized carbon or nitrogen atom, and d and h are each, independently, 0 or 1.

In one embodiment of the compounds of Formula 3, R₁ is a mono- or polycyclic aryl or heteroaryl, oligo- or monosaccharide group which is substituted with at least one electronegative atom or electronegative group. The mono- or polycyclic aryl or heteroaryl group is preferably substituted with an acid functional group, such as alkyl-CO₂H; alkyl-SO₃H; alkyl-SO₂H; alkyl-PO₃H₂; alkyl-OSO₃H; where the alkyl group is preferably a C₁–C₄-alkyl group. In another embodiment, the electronegative atom or electronegative functional group is selected from the group consisting of alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; —CN; —NO₂; —ONO₂, —CNO, —SH, —CNS, nitroalkyl, N,N-dialkylaminosulfonyl, aminocarbonyl, alkoxycarbonyl, alkoxycarbonylalkyl, cyanocarbonylalkyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl, trichloromethyl, acetamido and halogen atoms. R₁ can also be an alkylamino, alkyl or alkoxy group which is substituted with at least one electronegative atom or functional group. For example, in one embodiment, R₁ is selected from the group consisting of —(CH₂)_(a)NO₂; —(CH₂)_(a)OH; —(CH₂)_(a)PO₃H₂; —(CH₂)_(a)SO₃H; —(CH₂)_(a)SO₂H; —O(CH₂)_(a)COOH; —O(CH₂)_(a)NO₂; —O(CH₂)_(a)PO₃H₂; —O(CH₂)_(a)SO₂H; —O(CH₂)_(a)SO₃H; —O(CH₂)_(a)OH; —NH(CH₂)_(a)COOH; —NH(CH₂)_(a)NO₂; —NH(CH₂)_(a)PO₃H₂; —NH(CH₂)_(a)SO₂H; -and NH(CH₂)_(a)SO₃H; where a is 1 to 12, preferably 1 to about 4.

In another embodiment of the compounds of Formula 3, R₁ is a phenyl group which is substituted by p-toluenesulfonamido or hydroxyl; or R₁ is a —NH(CH₂)_(a)OH group, where a is 1 to about 4; a carboxyalkyl group, for example, a linear or branched carboxy-C₁–C₈-alkyl group; an alkoxycarbonyl group, such as a linear or branched C₁–C₈-alkoxycarbonyl group or an alkylcarbonate group, such as a linear or branched C₁–C₈-alkylcarbonate group. In this embodiment, ring atom is an sp²-hybridized carbon atom, except for G, which is a nitrogen atom; R and R₂ are both O; and d, c and h are each 1.

Preferred compounds of Formula 3 are of the formula

where X and R₁ have the meanings given above for these variables in Formula 1, R₂ is O, CH₂ or NR₃, where R₃ is H, alkyl, preferably C₁–C₆-alkyl, or aryl, and rings 1 and 2 can, optionally, independently be further substituted. Suitable substituents include alkyl groups, preferably normal or branched C₁–C₆-alkyl groups and halogen atoms.

In another embodiment, the NGF/p75^(NTR) binding inhibitor is of Formula 2,

In Formula 2, D₁, D₂, E₁, E₂, E₃, E₄ and G are each, independently, an sp²-hybridized carbon or nitrogen atom. One of X₁ and X₂ is a hydrogen atom or absent, while the other is an electronegative atom or an electronegative functional group. R, R₂ and R₄ are each, independently, an electronegative atom or an electronegative functional group, such as O, S, CH₂, or NR₃, where R₃ is H, alkyl, preferably C₁–C₆-alkyl, or aryl, such as phenyl. R, R₂ and one of X₁ and X₂ can also each be, independently, an electronegative atom or functional group, such as alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl group or a fluorine, chlorine, bromine or iodine atom. Y is N, O, S, C-L or N-L, where L is H, alkyl, preferably C₁–C₆-alkyl, or an electronegative atom or functional group, such as, but not limited to, alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H, —OC(O)(OH); halomethyl, dihalomethyl or trihalomethyl groups or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. Z and Z₁ are each, independently, O, S, CH, C═O, N, NH, N-alkyl, N-cycloalkyl and N-P, where P is a carbohydrate moiety, such as a monosaccharide group, for example, a fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl or lyxosyl group. T₁, T₂ and T₃ are each, independently, an sp²- or sp³-hybridized carbon or nitrogen atom. When f is 0, T₃ can further have the meanings given for Z and Z₁, above. a, b, c, d, e, f and i are each 0 or 1, provided that at least one of b and c is 1; at least one of d and e is 1 and at least one of f and i is 1.

R₁ is a monocyclic or polycyclic aryl or heteroaryl, oligo- or monosaccharide, alkyl, cycloalkyl, arylalkyl alkylamino or alkoxy group which is substituted with at least one substituent selected from the group consisting of electronegative atoms and electronegative functional groups. Preferred monosaccharide groups include fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl and lyxosyl groups. The electronegative substituent can be bonded to the aryl or heteroaryl ring system, or monosaccharide group either directly or indirectly via a bridging group, for example, an alkylene group such as a C₁–C₄-alkylene group or an oxaalkylene group. Suitable directly bonded and alkylene bridged electronegative atoms and functional groups include, but are not limited to, alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; —OH; —CN; —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —NO₂; —ONO₂, —CNO, —SH, —CNS, —OSO₃H; —OC(O)(OH); carboxyalkyl, nitroalkyl, N,N-dialkylaminosulfonyl, aminocarbonyl, alkoxycarbonyl, alkoxycarbonylalkyl, cyanocarbonylalkyl, haloalkyl, such as fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl or trichloromethyl; alkyamido or a halogen atom, such as a fluorine, chlorine, bromine or iodine atom. In one embodiment, R₁ is selected from the group consisting of groups including, but not limited to, —(CH₂)_(a)COOH; —(CH₂)_(a)NO₂; —(CH₂)_(a)OH; —(CH₂)_(a)PO₃H₂; —(CH₂)_(a)SO₃H; —(CH₂)_(a)SO₂H; —R₄(CH₂)_(a)COOH; —R₄(CH₂)_(a)NO₂; —R₄(CH₂)_(a)PO₃H₂; —R₄(CH₂)_(a)SO₂H; —R₄(CH₂)_(a)SO₃H; and —R₄(CH₂)_(a)OH, where a is 1 to 12, preferably 1 to about 4, and R₄ is NH or O.

Rings 1, 2 and 3 are each, independently, a five-or six-membered ring and, preferably, are each planar.

In another embodiment, the compound is of Formula 5,

wherein D₁, D₂, X₁, X₂, E₁, E₂, E₃, T₁, T₂, T₃, Z, G, R, R₁, R₂, R₄, b, c, e, f and i have the meanings given for these variables in Formula 2. Y₁, Y₂, and Y₃ are independently selected from the identities given for Y in Formula 2, and g and h are each, independently, 0 or 1. E₅ and E₆ are each, independently, an sp²-hybridized carbon or nitrogen atom, and g is 0 or 1. Ring 4 can be further unsubstituted or substituted with one or more substituents, such as alkyl or aryl groups.

In one embodiment of the compounds of Formulas 1, 2, 3 and 5, R₁ is selected from the group consisting of substituted phenylene, naphthylene, quinolylene and other substituted aromatic and heteroaromatic groups. R₁ can also be a substituted ethynyl or poly(ethynyl) group. Suitable identities for R₁ include, but are not limited to, the groups shown below.

In each of these groups, J can be any of the electronegative atoms or groups described in the definition of R₁ in Formulas 1 and 2. Preferably, J is selected from the group consisting of —OH, —CN, —NO₂, —CO₂H, —SO₃H, —SO₂H, —F, —Cl, —Br, —I, —PO₃H₂, —CF₃, —SO₂N(CH₃)₂, —C(O)NH₂, —C(O)CH₃, —C(O)OCH₃, —C(O)CN, —CH₂F, —CH₂Cl, —CF₂H, —CCl₂H, —CCl₃ and —NHC(O)CH₃; R₄ is NH or O, and n is an integer from 0 to about 6.

Preferred compounds of Formula 1 are represented by Formulas 6–14, 16–18, 21–30 and 32–34, below. Preferred compounds of Formula 3 are represented by Formulas 15, 19, 20 and 31 below.

In each of Formulas 6–34, R₁, X and Y have the meanings given above for these variables in Formula 1. In Formulas 6, and 9–15, Z is selected from the group consisting of O, S, NH, N-alkyl, N-cycloalkyl and N-P, wherein P is a carbohydrate moiety, preferably a monosaccharide moiety, such as a fucosyl, glucosyl, galactosyl, mannosyl, fructosyl, gulosyl, idosyl, talosyl, allosyl, altrosyl, ribosyl, arabinosyl, xylosyl or lyxosyl group. In Formulas 6, 7, 9, 10 and 12–17, R₂ is selected from the group consisting of O, S, CH₂ and NR₃, wherein R₃ is H, OH, aryl or alkyl.

Preferred compounds of Formulas 2 and 5 are of Formulas 35–49 below.

In Formula 32–46, the structural variables X, R₁, R₂, Z and Y each have the identities given previously for Formula 2.

In another embodiment, the NGF/p75^(NTR) binding inhibitor is of general formula 50,

In Formula 50, the structural variables D₁, D₂, X₁, X₂, E₁, E₂, E₃, T₁, T₂, T₃, Z, G, R, R₁, R₂, R₄, b, and c have the meanings given for these variables in Formula 2. T₃ is an sp²- or sp³-hybridized carbon or nitrogen atom, and is preferably an sp²-hybridized carbon or nitrogen atom.

A preferred subset of compounds of Formula 3 is represented by Formula 51,

In Formula 51, X, Y and R₁ each have the meanings given for these variables in Formula 1. R₂ is O, S, CH₂ or N—R₃, wherein R₃ is H, OH, alkyl, preferably normal or branched C₁–C₆-alkyl, or aryl, such as phenyl or substituted phenyl.

In a preferred embodiment, the NGF/p75^(NTR) inhibitor exhibits greater NGF/p75^(NTR) binding inhibition in cells which express p75^(NTR) but not trkA than in cells which express both p75^(NTR) and trkA. The binding of NGF to p75^(NTR) in cells which do not express trkA can, under certain conditions, mediate apoptotic cell death. The p75^(NTR) receptor has a greater affinity for NGF in this proapoptotic state, that is, in cells which do not express trkA. Compounds which exhibit greater NGF/p75^(NTR) binding inhibition in the absence of trkA advantageously selectively inhibit or interfere with processes such as apoptotic cell death, while having a smaller effect on other p75^(NTR)-mediated processes.

Preferred compounds which selectively inhibit the binding of NGF to p75^(NTR) in cells which do not express trkA include compounds of Formulas 52 and 53, below.

In Formulas 52 and 53, Q is selected from the group consisting of C₁–C₅-alkylene; para- and meta-phenylene; cycloalkylene, carbohydrate and para- and meta- —CH₂C₆H₄—. In Formulas 51 and 52, R₅, R₆ and R₇ are, preferably, each, independently, H, —COOH or —NO₂. More preferably, two of R₅, R₆ and R₇ are H and the other is —COOH or —NO₂.

The present invention also relates to a method of inhibiting the binding of NGF to p75^(NTR). The method comprises contacting NGF in the presence of p75^(NTR) with an NGF/p75^(NTR) binding inhibitory amount of a NGF/p75^(NTR) inhibitor compound, thereby inhibiting binding of NGF to p75^(NTR). The method can be practiced in vitro, for example, in a cell culture screening assay to screen compounds which potentailly bind, activate or inhibit receptor function. In such a method, the inhibitor compound can function by binding and eliminating any competing function of NGF in the sample or culture. The inhibitor compounds can also be used to control NGF activity in neuronal cell culture. The method can also be practised in vivo, for example, to inhibit one or more processes mediated by binding of NGF to p75^(NTR).

In another embodiment, the invention provides a method of treating a condition mediated by NGF/p75^(NTR) binding in a patient. The method comprises the step of administering to the patient a therapeutically effective amount of a NGF/p75^(NTR) binding inhibitor, such as any of the inhibitors described above. The condition to be treated can be any condition which is mediated, at least in part, by binding of NGF to the p75^(NTR) receptor. Such conditions include, but are not limited to, Alzheimer's disease, epilepsy, pain, multiple sclerosis, amyotrophic lateral sclerosis, stroke and cerebral ischemia.

Preferably, the NGF/p75^(NTR) binding inhibitor to be administered selectively inhibits the binding of NGF to p75^(NTR) in cells which do not express trkA. In this embodiment, the condition is mediated, at least in part, by the binding of NGF to the p75^(NTR) receptor in cells which do not express the trkA receptor. Generally, such conditions are mediated by NGF-induced apoptotic cell death.

The quantity of a given compound to be administered will be determined on an individual basis and will be determined, at least in part, by consideration of the individual's size, the severity of symptoms to be treated and the result sought. The NGF/p75^(NTR) binding inhibitor can be administered alone or in a pharmaceutical composition comprising the inhibitor, an acceptable carrier or diluent and, optionally, one or more additional drugs.

The NGF/p75^(NTR) binding inhibitor can be administered subcutaneously, intravenously, parenterally, intraperitoneally, intradermally, intramuscularly, topically, enteral (e.g., orally), rectally, nasally, buccally, sublingually, vaginally, by inhalation spray, by drug pump or via an implanted reservoir in dosage formulations containing conventional non-toxic, physiologically acceptable carriers or vehicles. The preferred method of administration is by oral delivery. The form in which it is administered (e.g., syrup, elixir, capsule, tablet, solution, foams, emulsion, gel, sol) will depend in part on the route by which it is administered. For example, for mucosal (e.g., oral mucosa, rectal, intestinal mucosa, bronchial mucosa) administration, nose drops, aerosols, inhalants, nebulizers, eye drops or suppositories can be used. The compounds and agents of this invention can be administered together with other biologically active agents, such as analgesics, anti-inflammatory agents, anesthetics and other agents which can control one or more symptoms or causes of a p75^(NTR)-mediated condition.

In a specific embodiment, it may be desirable to administer the agents of the invention locally to a localized area in need of treatment; this may be achieved by, for example, and not by way of limitation, local infusion during surgery, topical application, transdermal patches, by injection, by means of a catheter, by means of a suppository, or by means of an implant, said implant being of a porous, non-porous, or gelatinous material, including membranes, such as sialastic membranes or fibers. For example, the agent can be injected into the joints.

The compound of the invention can, optionally, be administered in combination with one or more additional drugs which, for example, are known for treating and/or alleviating symptoms of the condition mediated by p75^(NTR). The additional drug can be administered simultaneously with the compound of the invention, or sequentially.

The present invention also provides pharmaceutical compositions. Such compositions comprise a therapeutically (or prophylactically) effective amount of one or more NGF/p75^(NTR) binding inhibitors, preferably one or more compounds of Formulas 1, 2, 4 or 5, as described above, and a pharmaceutically acceptable carrier or excipient. Suitable pharmaceutically acceptable carriers include, but are not limited to, saline, buffered saline, dextrose, water, glycerol, ethanol, and combinations thereof. The carrier and composition can be sterile. The formulation should suit the mode of administration.

Suitable pharmaceutically acceptable carriers include but are not limited to water, salt solutions (e.g., NaCl), alcohols, gum arabic, vegetable oils, benzyl alcohols, polyethylene glycols, gelatin, carbohydrates such as lactose, amylose or starch, cyclodextrin, magnesium stearate, talc, silicic acid, viscous paraffin, perfume oil, fatty acid esters, hydroxymethylcellulose, polyvinyl pyrolidone, etc. The pharmaceutical preparations can be sterilized and if desired, mixed with auxiliary agents, e.g., lubricants, preservatives, stabilizers, wetting agents, emulsifiers, salts for influencing osmotic pressure, buffers, coloring, flavoring and/or aromatic substances and the like which do not deleteriously react with the active compounds.

The composition, if desired, can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. The composition can be a liquid solution, suspension, emulsion, tablet, pill, capsule, sustained release formulation, or powder. The composition can be formulated as a suppository, with traditional binders and carriers such as trilycerides. Oral formulation can include standard carriers such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, polyvinyl pyrollidone, sodium saccharine, cellulose, magnesium carbonate, etc.

The composition can be formulated in accordance with the routine procedures as a pharmaceutical composition adapted for intravenous administration to human beings. Typically, compositions for intravenous administration are solutions in sterile isotonic aqueous buffer. Where necessary, the composition may also include a solubilizing agent and a local anesthetic to ease pain at the site of the injection. Generally, the ingredients are supplied either separately or mixed together in unit dosage form, for example, as a dry lyophilized powder or water free concentrate in a hermetically sealed container such as an ampule or sachet indicating the quantity of active agent. Where the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water, saline or dextrose/water. Where the composition is administered by injection, an ampule of sterile water for injection or saline can be provided so that the ingredients may be mixed prior to administration.

The pharmaceutical compositions of the invention can also include an agent which controls release of the NGF/p75^(NTR) inhibitor compound, thereby providing a timed or sustained relase composition.

The present invention also relates to prodrugs of the NGF/p75^(NTR) binding inhibitors disclosed herein, as well as pharmaceutical compositions comprising such prodrugs. For example, compounds of the invention which include acid functional groups or hydroxyl groups can also be prepared and administered as a corresponding ester with a suitable alcohol or acid. The ester can then be cleaved by endogenous enzymes within the patient to produce the active agent.

In a further embodiment, the invention relates to the use of an NGF/p75^(NTR) binding inhibitor, such as any of the compounds described above, for treating a condition mediated by binding of NGF to p75^(NTR). The invention further relates to the use of these compounds for the manufacture of a medicament for treating a condition mediated by binding of NGF to p75^(NTR).

Representative syntheses of compounds of the invention are set forth in the following examples. Other synthetic pathways that can be used to prepare certain compounds of the invention are illustrated in FIGS. 3 and 4.

EXAMPLES Example 1 Synthesis of NGF/p75^(NTR) Inhibitors

General Methods

Reagents and solvents were obtained from commercial sources (Sigma, Aldrich, BDH). THF was dried by refluxing with benzophenone and potassium and subsequently distilled. All other solvents were utilized as they were received.

Thin layer chromatography (TLC) solvent systems used are given in Table 1. These were developed by ascending TLC on precoated aluminum backed sheets of silica gel 60 F254 (Merck). TLC plates were developed using ultra-violet light, iodine crystal and/or ninhydrin.

Melting points (mp) were determined on a Thomas Hoover Unimelt melting point apparatus and are uncorrected.

NMR spectra of final compounds were determined on an AVANCE 300 MHz NMR spectrometer. All NMR samples were prepared in DMSO-d6 unless otherwise indicated. Chemical shifts are reported as δ parts per million using DMSO as an internal reference. Mass spectrometric (MS) analyses are performed on a Varian Instrument VG Quattro multiple quadripole spectrometer using electrospray ionization (ESI). The spectra were all obtained in the negative ion mode. IR spectra were recorded on a Bomen MB-120 FT-IR spectrophotometer.

Abbreviations used herein are: HOAc, glacial acetic acid; THF, tetrahydrofiran; DMSO-d₆, deuterated dimethylsulfoxide; CHCl₃, chloroform: MeCN, acetonitrile; H₂O, distilled water; MeOH, methanol; EtOH, ethanol; TEA, triethylamine; EtOAc, ethyl acetate.

TABLE 1 List of Solvent Systems. Solvent Code Solvent System Solvent Ratio A MeOH:HOAc  5:1 B MeCN:H₂O:MeOH  8:1:1 C MeCN:H₂O:MeOH  4:1:1 D CHCl₃:MeOH:HOAc 95:10:3 E EtOH:HOAc 50:1 General Synthesis of Phthalimide Derivatives

Method A: The phthalimide series of compounds was prepared through the condensation of stoichiometric amounts of phthalic anhydride or a phthalic anhydride derivative (I) with an appropriate primary amine (II). The combined reagents were dissolved in glacial acetic acid, placed under a N₂ atmosphere and refluxed. The progress of the reaction was monitored by TLC. Final clear solutions were concentrated in vacuo and the resulting crude material was either reprecipitated from 1,4-dioxane/1N HCl or HOAc/H₂O and/or recrystallized from 95% ethanol, THF or 1,4-dioxane. In the instances where the final product precipitated out of the reaction solution, the completed reaction mixture was cooled to room temperature, the solid collected by filtration and washed with distilled water. This precipitate was reprecipitated with 1,4-dioxane/1N HCl or HOAc/H₂O and/or recrystallized from 95% ethanol, THF or 1,4-dioxane.

where X and R₁ are as previously defined.

Method B: Reaction conditions and purification procedures were similar to those of method A. However, instead of stoichiometric amounts of reagents, the anhydride (I) and the primary amine (II) were combined in a 1:2 ratio with the optional addition of 1 equivalent of anhydrous sodium acetate. During the course of preparing the various phthalimide derivatives, these reaction conditions were found to lead to increased product yields.

General Synthesis of Naphthalimide Derivatives

Method A: 1,8-naphthalic anhydride or its derivative (III) was reacted with an appropriate primary amine (II) under conditions similar to those of method A for the phthalimide series. Glacial acetic acid, dry THF, dry 1,4-dioxane or DMSO were used as solvents. Purification also included fractional recrystallisation.

Method B: As per method B for the phthalimide series. Glacial acetic acid was the only solvent used under these conditions.

General Synthesis of Amino Phthalimide or Amino Naphthalimide Derivatives

The amino-N-substituted phthalimides and amino-N-substituted naphthalimides were synthesized via the reduction of the corresponding nitro-N-substituted phthalimides or nitro-N-substituted naphthalimides with 10% palladium on activated charcoal in glacial acetic acid or glacial acetic acid/1,4-dioxane under a hydrogen atmosphere. Upon completion, as indicated by TLC, the catalyst was removed by filtering through a celite pad and the clear filtrate concentrated. The crude material was purified using procedures similar to those described above.

TABLE 2 Synthesized Phthalimide Derivatives

Cmpd. X R₁ Name 100 4-COOH CH₂COOH 4-carboxy-N-(1-carboxymethyl)phthalimide 101 4-COOH CH₂CH₂COOH 4-carboxy-N-(2-carboxyethyl)phthalimide 102 4-COOH CH₂(CH₂)₂COOH 4-carboxy-N-(3-carboxypropyl)phthalimide 103 4-COOH CH₂(CH₂)₃COOH 4-carboxy-N-(4-carboxybutyl)phthalimide 104 4-COOH CH₂(CH₂)₄COOH 4-carboxy-N-(5-carboxypentyl)phthalimide 105 4-COOH

4-carboxy-N-(p-carboxyphenyl)phthalimide 106 4-COOH

4-carboxy-N-(m-carboxyphenyl)phthalimide 107 4-COOH

4-carboxy-N-(o-carboxyphenyl)phthalimide 108 4-COOH

4-carboxy-N-(p-carboxyphenylmethyl)phthalimide 109 4-COOH

4-carboxy-N-phenylphthalimide 111 4-COOH

4-carboxy-N-aspartylphthalimide 120 3-NO₂ CH₂COOH 3-nitro-N-(1-carboxymethyl)phthalimide 121 3-NO₂ CH₂CH₂COOH 3-nitro-N-(2-carboxyethyl)phthalimide 122 3-NO₂ CH₂(CH₂)₂COOH 3-nitro-N-(3-carboxypropyl)phthalimide 123 3-NO₂ CH₂(CH₂)₃COOH 3-nitro-N-(4-carboxybutyl)phthalimide 124 3-NO₂ CH₂(CH₂)₄COOH 3-nitro-N-(5-carboxypentyl)phthalimide 125 3-NO₂

3-nitro-N-(p-carboxyphenyl)phthalimide 126 3-NO₂

3-nitro-N-(m-carboxyphenyl)phthalimide 127 3-NO₂

3-nitro-N-(o-carboxyphenyl)phthalimide 140 4-NO₂ CH₂COOH 4-nitro-N-(1-carboxymethyl)phthalimide 141 4-NO₂ CH₂CH₂COOH 4-nitro-N-(2-carboxyethyl)phthalimide 142 4-NO₂ CH₂(CH₂)₂COOH 4-nitro-N-(3-carboxypropyl)phthalimide 143 4-NO₂ CH₂(CH₂)₃COOH 4-nitro-N-(4-carboxybutyl)phthalimide 144 4-NO₂ CH₂(CH₂)₄COOH 4-nitro-N-(5-carboxypentyl)phthalimide 145 4-NO₂

4-nitro-N-(p-carboxyphenyl)phthalimide 146 4-NO₂

4-nitro-N-(m-carboxyphenyl)phthalimide 147 4-NO₂

4-nitro-N-(o-carboxyphenyl)phthalimide 165 4-NH₂

4-amino-N-(p-carboxyphenyl)phthalimide 166 4-NH₂

4-amino-N-(m-carboxyphenyl)phthalimide

TABLE 3 Synthesized Naphthalimide Derivatives

Compd. X R₁ Name 205 3-NO₂

3-nitro-N-(p-carboxyphenyl)-1,8-naphthalimide 206 3-NO₂

3-nitro-N-(m-carboxyphenyl)-1,8-naphthalimide 207 3-NO₂

3-nitro-N-(o-carboxyphenyl)-1,8-naphthalimide 208 3-NO₂

3-nitro-N-(p-carboxyphenylmethyl)-1,8-naphthalimide 209 3-NO₂

3-nitro-N-phenyl-1,8-naphthalimide 225 4-NO₂

4-nitro-N-(p-carboxyphenyl)-1,8-naphthalimide 226 4-NO₂

4-nitro-N-(m-carboxyphenyl)-1,8-naphthalimide 227 4-NO₂

4-nitro-N-(o-carboxyphenyl)-1,8-naphthalimide Synthesis of Phthalimide Derivatives: Method A:

4-carboxy-N-(carboxymethyl)phthalimide (100)

4-carboxyphthalic anhydride (benzene tricarboxylic acid anhydride) (1.0 g, 0.0052 mol), glycine (0.3907 g, 0.0052 mol) and 50–60 mls of glacial acetic acid were added to a 100 ml round-bottom flask equipped with a reflux condenser, heating mantle and stir plate. The system was placed under a N₂ atmosphere and heated to a gentle reflux. The progress of the reaction was monitored by TLC. After 7 hours the clear colourless solution was cooled to room temperature. The resulting white precipitate was filtered through a Buchner funnel and washed three times with 10 mls of distilled water. This crude material was recrystallized in EtOH/H₂O to afford the desired product as a powdery white solid. The filtrate was evaporated under vacuum using a rotary evaporator. The crude material was recrystallized from EtOH/H₂O to yield a second batch of white powdery product. Individual batches were dried in air for 24 hours and then in vacuo for 48–72 hours to afford 100 in a combined yield of 1.02 g (78%): mp=262–265° C.; R_(f) 0.70 (A): R_(f) 0.47 (B): R_(f) 0.20 (D): ¹H NMR (DMSO-d₆) δ 4.33 (s, 2H), 8.02 (d, J=7.8 Hz, 1H), 8.24 (bs, 1H), 8.36 (d, J=7.8 Hz, 1H); MS m/z (rel intensity) 249 (13), 248 (100), 204 (36); IR (cm⁻¹): 2750–3300 (OH), 3052 (C═CH), 2671 (C—H), 1776 (C═O), 1731 (C═O), 1705 (C═O), 1620 (C═C), 1420 (C═C), 1300 (C—O), 1122 (C—O), 746 (C═CH).

4-carboxy-N-(2-carboxyethyl)phthalimide (101)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and β-alanine (0.46, 0.0052 mol) were refluxed as above for 7 hours. Crystallisation of the product from EtOH yielded 1.37 g (78%) of 101 as a white solid: mp=240–242° C.; R_(f) 0.77 (A): R_(f) 0.67 (B): R_(f) 0.33 (D): ¹H NMR (DMSO-d₆); MS m/z (rel intensity) 263 (14), 262 (100); IR (cm⁻¹): 2800–3250 (OH), 3150 (C═CH), 2671 (C—H), 1777 (C═O), 1725 (C═O), 1705 (C═O), 1620 (C═C), 1452 (C═C), 1385(C—O), 1226 (C—O), 731 (C═CH). MS m/z (rel intensity) 263 (14), 262 (100).

4-carboxy-N-(3-carboxypropyl)phthalimide (102)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and 4-aminobutyric acid (0.54 g, 0.0052 mol) were refluxed as above for 7 hours. Crystallisation of the product from EtOH yielded 1.1 g (76%) of 102 as a white solid: mp=218–220° C.; R_(f) 0.78 (A): R_(f) 0.84 (C): R_(f) 0.28 (D): ¹H NMR (DMSO-d₆); IR (cm⁻¹): 2800–3250 (OH), 3050 (C═CH), 2680 (C—H), 1760 (C═O), 1712 (bs, C═O), 1560 (C═C), 1430 (C═C), 1397 (C—O), 1305 (C—O), 727 (C═CH); MS m/z (rel intensity) 277 (18), 276 (100).

4-carboxy-N-(4-carboxybutyl)phthalimide (103)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and 5-aminopentanoic acid (0.61 g, 0.0052 mol) were refluxed as above overnight. Crystallisation of the product from EtOH yielded 1.51 g (72%) of 103 as a white solid: mp=223° C.; R_(f) 0.79 (A): R_(f) 0.92 (C): R_(f) 0.36 (D): IR (cm⁻¹): 2750–3375 (OH), 3084 (C═CH), 2665 (C—H), 1767 (C═O), 1705 (bs, C═O), 1620 (C═C), 1486 (C═C), 1402 (CH₂), 1382 (C—O), 1302 (C—O), 732 (C═CH); MS m/z (rel intensity) 291 (15), 290 (100).

4-carboxy-N-(5-carboxypentyl)phthalimide (104)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and 6-aminohexanoic acid (0.68 g, 0.0052 mol) were refluxed as above overnight. Crystallisation of the product from EtOH yielded 1.35 g (85%) of 104 as a white solid: mp=202–204° C.; R_(f) 0.80 (A): R_(f) 0.84 (B): R_(f) 0.47 (D): IR (cm⁻¹): 2800–3250 (OH), 3103 (C═CH), 2675 (C—H), 1769 (C═O), 1709 (bs, C═O), 1625 (C═C), 1485 (C═C), 1403(C—O), 1303 (C—O), 730 (C═CH); MS m/z (rel intensity) 305 (16), 304 (100).

4-carboxy-N-(p-carboxyphenyl)phthalimide (105)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and p-aminobenzoic acid (0.714 g, 0.0052 mol) were refluxed as above overnight. A clean product from the mother liquor fraction was not obtained. Crystallisation of the precipitated product from MeOH/H₂O yielded 0.88 g (55%) of 105 as a white solid: mp=377–379° C.; R_(f) 0.90 (A): R_(f) 0.76 (B): R_(f) 0.46 (D): IR (cm⁻¹): 2750–3200 (OH), 3077 (C═CH), 2652 (C—H), 1777 (C═O), 1731 (C═O), 1699 (C═O), 1604 (C═C), 1512 (C═C), 1485 (C═C), 1428 (C═C), 1376 (C—O), 1310 (C—O), 1092 (C—O), 723 (C═CH); MS m/z (rel intensity) 311 (23), 310 (100).

4-carboxy-N-(m-carboxyphenyl)phthalimide (106)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and m-aminobenzoic acid (0.714 g, 0.0052 mol) were refluxed as above overnight. Crystallisation of the product from MeOH yielded 1.21 g (72%) of 106 as a white solid: mp=>380° C.; R_(f) 0.87 (A): R_(f) 0.75 (C): R_(f) 0.27 (D):IR (cm⁻¹): 2700–3125 (OH), 3090 (C═CH), 2665 (C—H), 1780 (C═O), 1731 (C═O), 1699 (C═O), 1610 (C═C), 1589 (C═C), 1484 (C═C), 1452 (C═C), 1383 (C—O), 1310 (C—O), 1222 (C—O), 722 (C═CH); MS m/z (rel intensity) 311 (22), 310 (100).

4-carboxy-N-(o-carboxyphenyl)phthalimide (107)

4-carboxyphthalic anhydride (1.0 g, 0.0052 mol) and m-aminobenzoic acid (0.714 g, 0.0052 mol) were refluxed as above for 24 hours. Crystallisation of the product from HOAc/H₂O yielded 0.96 g (59%) of 107 as a white solid: mp=262–264° C.; R_(f) 0.81 (A): R_(f) 0.77 (B): R_(f) 0.28 (D): ¹H NMR (DMSO-d₆) δ 7.55 (dd, J=7.8, 1.3 Hz, 1H), 7.64 (ddd, J=7.8, 7.8, 1.3 Hz, 1H), 7.78 (ddd, J=7.8, 7.8, 1.4 Hz), 8.06 (dd, J=7.8, 1.4 Hz, 1H), 8.09 (dd, J=7.7, 0.6 Hz, 1H), 8.32 (dd, J=7.7, 1.3 Hz, 1H), 8.117 (dd, J=1.3, 0.6 Hz, 1H); IR (cm⁻¹): 2800–3100 (OH), 3064 (C═CH), 2646 (C—H), 1779 (C═O), 1716 (bs, C═O), 1602 (C═C), 1493 (C═C), 1462 (C═C), 1385 (C—O), 1261 (C—O), 1217 (C—O), 722 (C═CH); MS m/z (rel intensity) 311 (20), 310 (100).

4-carboxy-N-(p-carboxyphenyl methyl)phthalimide (108)

4-carboxyphthalic anhydride (0.5 g, 0.0026 mol) and 4-(aminomethyl)benzoic acid (0.39 g, 0.0026 mol) were refluxed as above overnight. Crystallisation of the product from 1,4-dioxane/H₂O yielded 0.67 g (79%) of 108 as a white solid: mp=365–366° C.; R_(f) 0.76 (A): R_(f) 0.71 (C): R_(f) 0.50 (D): IR (cm⁻¹): 2800–3100 (OH), 3071 (C═CH), 2678 (C—H), 1782 (C═O), 1712 (bs, C═O), 1611 (C═C), 1577 (C═C), 1428 (C═C), 1391 (C—O), 1300 (C—O), 1105 (C—O), 734 (C═CH); MS m/z (rel intensity) 325 (20), 324 (100).

4-carboxy-N-aspartylphthalimide (111)

4-carboxyphthalic anhydride (0.5 g, 0.0026 mol) and L-aspartic acid (0.346 g, 0.0026 mol) were refluxed as above for 5 days. The clear colourless solution was concentrated under vacuum. The crude material was dissolved in EtOAc and extracted with water (3×25 ml). The EtOAc layer was dried over magnesium sulfate, concentrated under vacuum with a rotary evaporator and recrystallized in EtOAc/hexanes. The product was dried in air for 24 hours and then in vacuo for 48–72 hours to afford 0.15 g (19%) 111 as a powdery white solid: mp=242–243° C.; R_(f) 0.76 (A): R_(f) 0.52 (B): R_(f) (D): IR (cm⁻¹): 2750–3250 (OH), 3090 (C═CH), 2639 (C—H), 1783 (C═O), 1736 (bs, C═O), 1628 (C═C), 1485 (C═C), 1389 (bs, C—O), 1298 (C—O), 1196 (C—O), 729 (C═CH); MS m/z (rel intensity) 307 (156), 306 (100), 262 (29), 218 (49).

3-nitro-N-(1-carboxymethyl)phthalimide (120)

3-nitrophthalic anhydride (0.5 g, 0.0026 mol) and glycine (0.19 g, 0.0026 mol) were refluxed as above overnight. The clear solution was concentrated under vacuum with a rotary evaporator and the crude material triturated with hot 1,4-dioxane. Undissolved material was filtered through a Buchner funnel and washed twice with 1 ml hot 1,4-dioxane. The filtrate was diluted with water. A white solid appeared which was filtered through a Buchner and washed three times with 3–5 ml water. The product was dried in air for a short time and then in vacuo for 48–72 hours to afford 0.52 g (81%) 120 as off white crystals: mp=200–202° C.; R_(f) 0.73 (A): R_(f) 0.77 (C): R_(f) 0.23 (D): IR (cm⁻¹): 2800–3200 (OH), 3096 (C═CH), 2652 (C—H), 1779 (C═O), 1724 (C═O), 1690 (C═O), 1648 (C═C), 1544 (N═O), 1470 (C═C), 1448 (C═C), 1412 (C—O), 1368 (N═O), 1260 (C—O), 722 (C═CH); MS m/z (rel intensity) 250 (15), 249 (100), 205 (89).

3-nitro-N-(2-carboxyethyl)phthalimide (121)

3-nitrophthalic anhydride (0.5 g, 0.0026 mol) and β-alanine (0.23 g, 0.0026 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.55 g (80%) 121 as a pale yellow powder: mp=146–148° C.; R_(f) 0.73 (A): R_(f) 0.87 (C): R_(f) 0.57 (D): ¹H NMR (DMSO-d₆) δ 2.60 (t, J=7.4 Hz, 2H), 3.78 (t, J=7.4 Hz, 2H), 8.07 (dd, J=7.5, 8.0 Hz, 1H), 8.16 (d, J=7.5 Hz, 1H), 8.27 (d, J=8.0, 1H); IR (cm⁻¹): 2800–3200 (OH), 3097 (C═CH), 2620 (C—H), 1781 (C═O), 1725 (bs, C═O), 1617 (C═C), 1545 (N═O), 1468 (C═C), 1450 (C═C), 1395 (C—O), 1360 (N═O), 1235 (C—O), 723 (C═CH); MS m/z (rel intensity) 264 (76), 263 (100), 191 (90).

3-nitro-N-(3-carboxypropyl)phthalimide (122)

3-nitrophthalic anhydride (0.5 g, 0.0026 mol) and 4-aminobutyric acid (0.268 g, 0.0026 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.57 g (79%) 122 as a very pale orange powder: mp=144–146° C.; R_(f) 0.62 (A): R_(f) 0.87 (C): R_(f) 0.78(D): IR (cm⁻¹): 3000–3250 (OH), 3219 (C═CH), 2953 (C—H), 1778 (C═O), 1716 (C═O), 1667 (C═O), 1615 (C═C), 1548 (N═O), 1442 (C═C), 1395 (C—O), 1355 (N═O), 1189 (C—O), 723 (C═CH); MS m/z (rel intensity) 313 (100), 278 (65), 277 (42), 191 (71).

3-nitro-N-(4-carboxybutyl)phthalimide (123)

3-nitrophthalic anhydride (0.5 g, 0.0026 mol) and 5-aminopentanoic acid (0.30 g, 0.0026 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.55 g (73%) 123 as pale yellow flat crystals: mp=158–160° C.; R_(f) 0.69 (A): R_(f) 0.90 (C): R_(f) 0.73 (D): ¹H NMR (DMSO-d₆) δ 1.53 (m, 2H), 1.58 (m, 2H), 2.24 (t, J=7.1 Hz, 2H), 3.57 (t, J=6.7 Hz, 2H), 8.04 (dd, J=8.0, 7.5 Hz, 1H), 8.16 (d, J=7.5 Hz, 1H), 8.27 (d, J=8.0 Hz, 1H); IR (cm⁻¹): 2800–3130 (OH), 3096 (C═CH), 2691 (C—H), 1774 (C═O), 1723 (bs, C═O), 1616 (C═C), 1543 (N═O), 1466 (C═C), 1443 (C═C), 1396 (C—O), 1358 (N═O), 1209 (C—O), 1050 (C—O), 722 (C═CH); MS m/z (rel intensity) 291 (92), 247 (31), 191 (100).

3-nitro-N-(5-carboxypentyl)phthalimide (124)

3-nitrophthalic anhydride (0.5 g, 0.0026 mol) and 6-aminohexanoic acid (0.34 g, 0.0026 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.75 g (95%) 124 as a pale yellow powder: mp=144° C.; R_(f) 0.68 (A): R_(f) 0.89 (C): R_(f) 0.71 (D): IR (cm⁻¹): 2800–3180 (OH), 3096 (C═CH), 2620 (C—H), 1777 (C═O), 1723 (bs, C═O), 1617 (C═C), 1543 (N═O), 1468 (C═C), 1442 (C═C), 1395 (C—O), 1359 (N═O), 1057 (C—O), 723 (C═CH); MS m/z (rel intensity) 305 (100), 191 (17).

3-nitro-N-(p-carboxyphenyl)phthalimide (125)

3-nitrophthalic anhydride (0.79 g, 0.0041 mol) and p-aminobenzoic acid (0.56 g, 0.0041 mol) were refluxed as above overnight. Concentration of the solution under vacuum by rotary evaporator and crystallisation of the product from EtOH/H₂O yielded 1.1 g (68%) of 125 as a vibrant light yellow powder: mp=338–340° C.; R_(f) 0.76 (A): R_(f) 0.89 (C): R_(f) 0.66 (D): R (cm⁻¹): 2750–3125 (OH), 3091 (C═CH), 2671 (C—H), 1782 (C═O), 1736 (C═O), 1693 (C═O), 1610 (C═C), 1585 (C═C), 1529 (N═O), 1513 (C═C), 1433 (C═C), 1378 (C—O), 1360 (N═O), 1291 (C—O), 766 (C═CH); MS m/z (rel intensity) 311 (100), 267 (25), 191 (15).

3-nitro-N-(m-carboxyphenyl)phthalimide (126)

3-nitrophthalic anhydride (0.79 g, 0.0041 mol) and m-aminobenzoic acid (0.56 g, 0.0041 mol) were refluxed as above overnight. Concentration of the solution under vacuum by rotary evaporator and crystallisation of the product from EtOH/H₂O yielded 1.23 g (76%) of 126 as a vibrant yellow powder: mp=354–355° C.; R_(f) 0.77 (A): R_(f) 0.84 (C): R_(f) 0.54 (D): IR (cm⁻¹): 2740–3100 (OH), 3088 (C═CH), 2665 (C—H), 1776 (C═O), 1725 (bs, C═O), 1614 (C═C), 1542 (N═O), 1460 (C═C), 1420 (C═C), 1382 (C—O), 1356 (N═O), 1120 (C—O), 717 (C═CH); MS m/z (rel intensity) 311 (100), 267 (65), 191 (60).

3-nitro-N-(o-carboxyphenyl)phthalimide (127)

3-nitrophthalic anhydride (1.0 g, 0.0052 mol) and o-aminobenzoic acid (0.71 g, 0.0052 mol) were refluxed as above for four days. The clear solution was purified as per 120 to yield 0.34 g (21%) 127 as pale orange grains: mp=190–192° C.; R_(f) 0.74 (A): R_(f) 0.87 (C): R_(f) 0.62 (E): IR (cm⁻¹): 2700–3300 (OH), 3093 (C═CH), 2620 (C—H), 1718 (C═O), 1681 (bs, C═O), 1609 (C═C), 1592 (C═O), 1534 (N═O), 1482 (C═C), 1451 (C═C), 1360 (N═O), 1316 (C—O), 1257 (C—O), 771 (C═CH); MS m/z (rel intensity) 311 (50), 285 (100), 241 (55), 122 (45).

4-nitro-N-(1-carboxymethyl)phthalimide (140)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and glycine (0.097 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.28 g (86%) 140 as very pale yellow crystals: mp=195–96° C.; R_(f) 0.79 (A): R_(f) 0.75 (B): R_(f) 0.28 (D): IR(cm⁻¹): 2811–3150 (OH), 3115 (C═CH), 1787 (C═O), 1730 (bs, C═O), 1622 (C═C), 1551 (N═O), 1412 (C═C), 1391 (C—O), 1351 (N═O), 1117 (C—O), 720 (C—CH); MS m/z (rel intensity) 250 (7), 249 (62), 205 (100), 122 (10).

4-nitro-N-(2-carboxyethyl)phthalimide (141)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and β-alanine (0.115 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.31 g (90%) 141 as a very pale yellow powder: mp=206–208° C.; R_(f) 0.84 (A): R_(f) 0.81 (B): R_(f) 0.55 (D): IR (cm⁻¹): 2800–3125 (OH), 3109 (C═CH), 2646 (C—H), 1780 (C═O), 1718 (bs, C═O), 1621 (C═C), 1536 (N═O), 1441 (C═C), 1395 (C—O), 1346 (N═O), 1228 (C—O), 724 (C═CH); MS m/z (rel intensity) 263 (100), 191 (36).

4-nitro-N-(3-carboxypropyl)phthalimide (142)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and 4-aminobutyric acid (0.134 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.35 g (98%) 142 as very pale yellow powder: mp=176–178° C.; R_(f) 0.82 (A): R_(f) 0.83 (B): R_(f) 0.71 (D): IR (cm⁻¹): 3000–3300 (OH), 3122 (C═CH), 1775 (C═O), 1707 (bs, C═O), 1617 (C═C), 1545 (N═O), 1446 (C═C), 1399 (C—O), 1349 (N═O), 1167 (C—O), 722 (C—CH); MS m/z (rel intensity) 291 (100), 191 (8).

4-nitro-N-(4-carboxybutyl)phthalimide (143)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and 5-aminopentanoic acid (0.152 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.37 g (98%) 143 as dull white crystals: mp=172° C.; R_(f) 0.93 (A): R_(f) 0.83 (B): R_(f) 0.69 (D): ¹H NMR (DMSO-d₆) δ 1.83 (m, 2H), 2.29 (t, J=7.2 Hz, 2H), 3.64 (t, J=6.7 Hz, 2H), 8.01 (d, J=7.6 Hz, 1H), 8.45 (d, J=1.9 Hz, 1H), 8.59 (dd, J=7.6, 1.9 Hz, 1H); IR (cm⁻¹): 2750–3200 (OH), 3056 (C═CH), 2620 (C—H), 1773 (C═O), 1707 (bs, C═O), 1624 (C═C), 1543 (N═O), 1438 (C═C), 1403 (C—O), 1351 (N═O), 1217 (C—O), 1068 (C—O), 723 (C═CH); MS m/z (rel intensity) 305 (100).

4-nitro-N-(5-carboxypentyl)phthalimide (144)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and 6-aminohexanoic acid (0.177 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.39 g (97%) 144 as very pale dull orange crystals: mp=140° C.; R_(f) 0.86 (A): R_(f) 0.85 (B): R_(f) 0.75 (D): IR (cm⁻¹): 2875–3125 (OH), 3064 (C═CH), 1775 (C═O), 1706 (bs, C═O), 1624 (C═C), 1544 (N═O), 1437 (C═C), 1398 (C—O), 1348 (N═O), 1069 (C—O), 722 (C═CH); MS m/z (rel intensity) 277 (100), 251 (11), 191 (124).

4-nitro-N-(p-carboxyphenyl)phthalimide (145)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and p-aminobenzoic acid (0.18 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.33 g(81%) 145 as a very pale dull yellow powder: mp=331–332° C.; R_(f) 0.86 (A): R_(f) 0.92 (C): R_(f) 0.56 (D): IR(cm⁻¹): 2750–3150 (OH), 3116 (C═CH), 2684 (C—H), 1780 (C═O), 1730 (bs, C═O), 1622 (C═C), 1608 (C═C), 1543 (N═O), 1510 (C═C), 1434 (C═C), 1383 (C—O), 1350 (N═O), 1103 (C—O), 727 (C═CH); MS m/z (rel intensity) 311 (100), 267 (87).

4-nitro-N-(m-carboxyphenyl)phthalimide (146)

4-nitrophthalic anhydride (0.25 g, 0.0013 mol) and m-aminobenzoic acid (0.18 g, 0.0013 mol) were refluxed as above overnight. The clear solution was purified as per 120 to yield 0.30 g (74%) 146 as a very pale dull yellow powder: mp=368–370° C.; R_(f) 0.83 (A): R_(f) 0.93 (C): R_(f) 0.53 (D): IR (cm⁻¹): 2700–3280 (OH), 3122 (C═CH), 2687 (C—H), 1781 (C═O), 1727 (bs, C═O), 1622 (C═C), 1588 (C═C), 1546 (N═O), 1461 (C═C), 1420 (C═C), 1386 (C—O), 1350 (N═O), 1113 (C—O), 727 (C═CH); MS m/z (rel intensity) 311 (68), 285 (46), 267 (46), 191 (100).

4-nitro-N-(o-carboxyphenyl)phthalimide (147)

4-nitrophthalic anhydride (0.5 g, 0.0026 mol) and o-aminobenzoic acid (0.36 g, 0.0026 mol) were refluxed as above for four days. The clear solution was purified as per 120 with an additional final crystallisation from acetone/H₂O to yield 0.12 g (15%) 147 as a very pale dull yellow powder: mp=242–243° C.; R_(f) 0.80 (A): R_(f) 0.88 (C): R_(f) 0.49 (D): IR (cm⁻¹): 2725–3100 (OH), 3071 (C═CH), 2646 (C—H), 1786 (C═O), 1730 (C═O), 1693 (C═O), 1620 (C═C), 1601 (C═C), 1538 (N═O), 1491 (C═C), 1452 (C═C), 1383 (C—O), 1345 (N═O), 1123 (C—O), 723 (C═CH); MS m/z (rel intensity) 311 (33), 267 (76), 241 (54), 136 (100).

Method B:

4-carboxy-N-phenylphthalimide (109)

4-carboxyphthalic anhydride (benzene tricarboxylic acid anhydride) (1.0 g, 0.0052 mol), aniline (0.96 g, 0.0104 mol), and 70–80 mls of glacial acetic acid were added to a 100 ml round-bottom flask equipped with a reflux condenser, heating mantle and stir plate. The system was placed under a N₂ atmosphere. A white solid precipitated out of the clear pale yellow solution within 1 minute. The mixture was heated to a gentle reflux. More precipitate formed during the course of the reaction. After 12 hours the mixture was cooled to room temperature and concentrated under vacuum with a rotary evaporator. The crude material was reprecipitated in 1,4-dioxane and IN HCl. The resultant white precipitate was filtered through a Buchner funnel and washed three times with 15 ml of water. The product was dried in air for 24 hours and then in vacuo for 48–72 hours to afford 1.25 g (90%) 109 as a white fluffy solid: mp=257–258° C.; R_(f) 0.83 (A): R_(f) 0.76 (B): R_(f) 0.62 (D): IR (cm⁻¹): 2800–3125 (OH), 3071 (C═CH), 2665 (C—H), 1788 (C═O), 1719 (bs, C═O), 1602 (C═C), 1596 (C═C), 1504 (C═C), 1487 (C═C), 1399 (C—O), 1124 (C—O), 724 (C═CH); MS m/z (rel intensity) 267 (16), 266 (100).

Synthesis of Amino-Phthalimide Derivatives

4-amino-N-(p-carboxyphenyl)phthalimide (165)

4-nitro-N-(p-carboxyphenyl)phthalimide (145) (0.2 g, 0.6 mmol) partially dissolved in 30 ml of 1,4-dioxane and 2 ml HOAc was added to a three necked round bottom flask equipped with a rubber septum, a gas inlet adapter and an adapter tightly fitted with a balloon. After the reaction vessel was purged three times with N₂, 0.02 g of 10% Pd on activated charcoal was added. The reaction vessel was then flushed three times with H₂. The heterogenous mixture was vigorously stirred under a hydrogen atmosphere overnight. The catalyst was removed by filtration through a celite pad and the filtrate concentrated under vacuum to give a bright yellow solid. The crude material which contained unreacted nitro compound was resubjected to the above procedure. Resulting crude material was triturated with hot 1,4-dioxane and undissolved material removed by filtration. The filtrate was diluted with water. The ensuing solid was filtered through a Buchner funnel and washed three times with 1 ml water. The product was dried in air for a short time and then in vacuo for 48–72 hours to afford 0.071 g (39%) 165 as a dark yellow solid: mp=270–271° C.; R_(f) 0.88 (A): R_(f) 0.80 (C): R_(f) 0.49 (D): IR (cm⁻¹): 3366 (NH), 3193 (NH), 2750–3200 (OH), 3075 (C═CH), 2669 (C—H), 1767 (C═O), 1752 (C═O), 1701 (bs, C═O), 1637 (C═C), 1607 (C═C), 1514 (C═C), 1482 (C═C), 1370 (C—N), 1220 (C—O), 740 (C═CH); MS m/z (rel intensity) 282 (16), 281 (100), 237 (71) 120 (43).

4-amino-N-(m-carboxyphenyl)phthalimide (166)

4-nitro-N-(m-carboxyphenyl)phthalimide (145) (0.2 g, 0.6 mmol) was catalytically hydrogenated as 165. Crystallization from 1,4-dioxane/1N HCl to yield 0.091 g (50%) of 166 as a dark orange solid: mp=306–308° C.; R_(f) 0.81 (A): R_(f) 0.79 (B): R_(f) 0.50 (D): ¹H NMR (DMSO-d₆) δ 6.57 (bs, 2H), 7.05 (d, J=8.0 Hz, 1H), 7.06 (d, J=7.2 Hz, 1H), 7.50 (dd, I=7.2, 8.0 Hz, 1H), 7.67 (m, 2H), 7.97 (m, 2H);IR (cm⁻¹): 3393 (NH), 3193 (NH), 2750–3125 (OH), 3082 (C═CH), 2669 (C—H), 1755 (C═O), 1707 (bs, C═O), 1643 (C═C), 1587 (C═C), 1458 (C═C), 1406 (C═C), 1372 (C—N), 1221 (C—O), 755 (C═CH); MS m/z (rel intensity) 317 (100) 282 (15), 281 (93), 233 (44) 161 (33).

Synthesis of Naphthalimide Derivatives:

Method A:

3-nitro-N-(p-carboxyphenyl)-1,8-naphthalimide (205)

3-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and p-aminobenzoic acid (0.28 g, 0.0020 mol) were refluxed in dry (distilled from CaH₂) 1,4-dioxane as per 100 for seven days. The dark orange brown solution was diluted with water until a beige precipitate formed. The precipitate was filtered through a Buchner funnel and washed with water. The crude material was reprecipitated from 1,4-dioxane/1N HCl and filtered. Successive fractional recrystallisations in CHCl₃ afforded 0.17 g (23%) 205 as an orange amber solid: mp=362–364° C.; R_(f) 0.80 (A): R_(f) 0.88 (B): R_(f) 0.36 (D): IR (cm⁻¹): 2500–3150 (OH), 3079 (C═CH), 2671 (C—H), 1783 (C═O), 1716 (C═O), 1678 (bs, C═O), 1628 (C═C), 1597 (C═C), 1539 (N═O), 1419 (C═C), 1338 (N—O), 1243 (C—O), 787 (C═CH); MS m/z (rel intensity) 361 (100) 317 (52).

3-nitro-N-(m-carboxyphenyl)-1,8-naphthalimide (206)

3-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and m-aminobenzoic acid (0.28 g, 0.0020 mol) were refluxed and the final solution was manipulated as per 205. Crystallization from 1,4-dioxane afforded 0.28 g (39%) of 206 as an yellow amber solid: mp=342–344° C.; R_(f) 0.77 (A): R_(f) 0.90 (B): R_(f) 0.56 (D): IR (cm⁻¹): 2800–3125 (OH), 3091 (C═CH), 2623 (C—H), 1739 (C═O), 1711 (bs, C═O), 1677 (C═O), 1628 (C═C), 1599 (C═C), 1546 (N═O), 1449 (C═C), 1420 (C═C), 1341 (N—C), 1245 (C—O), 791 (C═CH); MS m/z (rel intensity) 361 (100) 317 (30).

3-nitro-N-(o-carboxyphenyl)-1,8-naphthalimide (207)

3-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and o-aminobenzoic acid (0.28 g, 0.0020 mol) were refluxed and the final solution was manipulated as per 205. Crystallization from 1,4-dioxane afforded 0.21 g (29%) of 207 as an orange amber solid: mp=234–237° C.; R_(f) 0.80 (A): R_(f) 0.80 (B): R_(f) 0.64 (D): IR (cm⁻¹): 2850–3155 (OH), 3071 (C═CH), 2626 (C—H), 1717 (bs, C═O), 1668 (C═O), 1625 (C═C), 1599 (C═C), 1542 (N═O), 1490 (C═C), 1422 (C═C), 1339 (N—O), 1248 (C—O), 789 (C═CH); MS m/z (rel intensity) 361 (100).

3-nitro-N-(p-carboxyphenylmethyl)naphthalimide (208)

3-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and 4-(aminomethyl)benzoic acid (0.31 g, 0.0020 mol) were refluxed as per 100 overnight. Precipitate that formed during the course of the reaction was filtered and washed with water. A clean product from the mother liquor fraction was not obtained. Crystallization of the product from 1,4-dioxane/H₂O yielded 0.30 g (39%) of 208 as a beige powder: mp=334–336° C.; R_(f) 0.89 (A): R_(f) 0.71 (C): R_(f) 0.77 (D): IR (cm⁻¹): 2800–3130 (OH), 3084 (C═CH), 2671 (C—H), 1789 (C═O), 1707 (bs, C═O), 1666 (C═O), 1628 (C═C), 1598 (C═C), 1539 (N═O), 1450 (C═C), 1425 (C═C), 1343 (N—C), 1296 (C—O), 788 (C═CH); MS m/z (rel intensity) 375 (100), 331 (48), 172 (57).

4-nitro-N-(p-carboxyphenyl)-1,8-naphthalimide (225)

4-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and p-aminobenzoic acid (0.28 g, 0.0020 mol) were refluxed as per 100 for 48 hours. Precipitate that formed during the course of the reaction was filtered and washed with water. A clean product from the mother liquor fraction was not obtained. Crystallization from 1,4-dioxane/1N HCl afforded 0.26 g (35%) of 225 as a beige solid: mp=>320° C.; R_(f) 0.89 (A): R_(f) 0.82 (B): R_(f) 0.42 (D); ¹H NMR (DMSO-d₆) δ 7.55 (d, J=8.3 Hz, 2H), 8.09 (d, J=8.3 Hz, 2H), 8.13 (dd, J=8.4, 7.7 Hz, 1H), 8.61 (m, 3H), 8.76 (d, J=8.4 Hz, 1H); IR (cm⁻¹): 2800–3100 (OH), 3079 (C═CH), 2674 (C═H), 1713 (C═O), 1678 (bs, C═O), 1625 (C═C), 1607 (C═C), 1584 (C═C), 1532 (N═O), 1426 (C═C), 1412 (C═C), 1368 (C—O), 1346 (N—O), 1237 (C—O), 785 (C═CH); MS m/z (rel intensity) 362 (22), 361 (100).

4-nitro-N-(m-carboxyphenyl)-1,8-naphthalimide (226)

4-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and p-aminobenzoic acid (0.28 g, 0.0020 mol) were refluxed as per 100 for 48 hours. Precipitate that formed during the course of the reaction was filtered and washed with water. The dark amber filtrate was concentrated to 20 ml in vacuo and diluted with 1N HCl until a beige precipitate formed. The precipitate was filtered through a Buchner funnel and washed with water. Crystallization from 1,4-dioxane/H₂O afforded 0.59 g (81%) of 226 as a beige solid: mp=>320° C.; R_(f) 0.86 (A): R_(f) 0.82 (B): R_(f) 0.48 (D): ¹H NMR (DMSO-d₆) δ 7.68 (m, 2H), 8.05 (m, 2H), 8.13 (dd, J=8.6, 8.4 Hz, 1H), 8.61 (m, 3H), 8.76 (dd, J=8.4, 0.8 Hz, 1H); IR (cm⁻¹): 2750–3125 (OH), 3075 (C═CH), 2664 (C═H), 1697 (bs, C═O), 1625 (C═C), 1584 (C═C), 1530 (N═O), 1456 (C═C), 1424 (C═C), 1369 (C—O), 1350 (N—O), 1237 (C—O), 784 (C═CH); MS m/z (rel intensity) 362 (22), 361 (100).

Method B:

3-nitro-N-phenyl-1,8-naphthalimide (209)

3-nitro-1,8-naphthalic anhydride (0.5 g, 0.0020 mol) and aniline (0.38 g, 0.0041 mol) were reacted and purified as per 109. Crystallization from CHCl₃ afforded 0.38 g (60%) 209 as a beige solid: mp=264–266° C.; R_(f) 0.81 (A): R_(f) 0.89 (C): R_(f) 0.77 (D): IR (cm⁻¹): 3085 (C═CH), 2670 (C—H), 1713 (C═O), 1667 (bs, C═O), 1596 (C═C), 1542 (N═O), 1509 (C═C), 1416 (C═C), 1335 (N—O), 1244 (C—O), 707 (C═CH); MS m/z (rel intensity) 319 (15), 217 (100) 199 (34) 129 (57).

Example 2 Assessment of NGF/p75^(NTR) Binding Inhibition

The radio-iodination and receptor binding of NGF (Sutter et al., 1979) was performed with modifications (Ross et al., 1997) as follows: Evaluation of the ability of NCP compounds to inhibit TrkA and p75^(NTR) binding was determined by the binding of ¹²⁵I-NGF to PC12 cells (rat pheochromocytoma cells expressing TrkA and p75^(NTR); obtained from ATCC) and PC12^(nnr5) (rat pheochromocytoma cells expressing p75^(NTR) only; obtained from Dr. L. Greene, Columbia University, NY). The p75^(NTR) is in a low affinity state and a high affinity state, respectively, in these cell types (Ross et al., 1998). PC12 and PC12^(nnr5) cells were grown in RPMI (Sigma) with 10% heat inactivated donor horse serum and 5% fetal calf serum. Cells were harvested by replacing the medium with calcium, magnesium-free balanced salt solution (Gey's solution) and incubating at 37° C. for 15 minutes. Cells were pelleted by centrifugation and suspended in HKR buffer (10 mM Hepes [pH 7.35] containing 125 mM NaCl, 4.8 mM KCl, 1.3 mM CaCl₂, 1.2 mM MgSO₄, 1.2 mM KH₂PO₄, 1 g/L glucose and 1 g/L BSA) at a cell concentration of 2×10⁶/mL and kept at 4° C. Triplicate tubes were set up for total binding, non-specific binding and binding in the presence of candidate competitor molecule (i.e., a tube for each data point). Each tube contained ¹²⁵I-NGF (at 1 nM), 400,000 cells (for a final cell concentration of 10⁶/mL) and NGF (50 nM, to define non-specific binding), as required. The tubes were incubated for 2 h at 4° C. and specific binding evaluated by measuring specifically bound DPM (Ross et al., 1997). Data were analysed and the results expressed as receptor binding observed in the presence of competitor (e.g. NCP compounds) as a percentage of receptor binding in the absence of a competitor.

Com- pound PC12 nnr5 (50 μM) % of Max % of Max 100 102, 108, 137 Avg = 116 108, 111, 80 Avg = 100 101 89, 94, 139 = 107 89, 91, 64 = 81 102 79, 80, 113 = 91 55, 50, 61 = 55 103 69, 65, 100 = 78 32, 69, 41 = 47 104 51, 50, 66 = 56 30, 65, 17 = 37 105 29, 38, 40 = 36 31, 17, 55 = 34 106 40, 40, 52 = 44 37, 16, 24 = 26 107 111, 86, 103 = 100 58, 113, 83 = 85 107a 101, 116, 110 = 109 67, 115, 78 = 87 108 90, 55, 75 = 73 135, 77, 66 = 93 109 50, 60, 57 = 56 70, 74, 75 = 73 111 90, 96, 101 = 96 67, 70, 111 = 83 120 133, 92, 103 = 109 218, 200, 130 = 183 121 121, 92, 103 = 103 204, 188, 103 = 165 122 106, 88, 98 = 97 232, 152, 104 = 163 123 118, 75, 98 = 97 172, 161, 117 = 150 124 117, 71, 89 = 92 166, 182, 110 = 153 125 83, 87, 99 = 90 47, 54, 47 = 49 126 90, 69, 72 = 77 34, 54, 69 = 52 127 140, 101, 114 = 118 136, 129, 71 = 112 140 100, 126, 108 = 111 89, 108, 100 = 99 141 74, 108, 87 = 90 98, 114, 77 = 96 142 55, 77, 67 = 66 52, 51, 51 = 51 143 65, 97, 72 = 78 76, 79, 71 = 75 144 68, 89, 77 = 78 74, 70, 74 = 73 145 60, 77, 73 Avg = 70 76, 86, 71 Avg = 78 146 52, 52, 71 = 58 48, 43, 42 = 44 165 54, 53, 40 = 49 61, 53, 68 = 61 166 43, 58, 71 = 57 55, 64, 56 = 58 205 16, 19, 15 = 17 0, 11, 15 = 9 206 25, 29, 35 = 30 20, 17, 33 = 23 207 60, 34, 69 = 54 64, 52, 59 = 58 208 56, 45, 47 = 49 103, 87, 58 = 83 209 NS NT NT 225 NS 69, 60, 68 = 66 49, 50, 68 = 56 226 NS 27, 29, 35 = 30 13, 10, 13 = 12 NS: Not Soluble @ 100 μM DMSO NT: Not Tested

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

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1. A compound of Formula 3 which is:

or a pharmaceutically acceptable salt thereof, wherein: one of X₁ and X₂ is hydrogen and the other of X₁ and X₂ is selected from the group comprising of carbonyl; thiocarbonyl; ester; imino; amido; carboxylic acid; sulfonic acid; sulfinic acid; sulfamic acid; phosphonic acid; boronic acid; sulfate ester, hydroxyl; mercapto; cyano; cyanate; thiocyanate; isocyanate; isothiocyanate; carbonate; nitrate; nitro; alkylcarbonyl; alkylthiocarbonyl; alkoxycarbonyl; aminocarbonyl; halomethyl; dihalomethyl; trihalomethyl; and a halogen atom; and R₁ is selected from the group consisting of a monocyclic aryl substituted with at least one acid functional group, a polycyclic aryl substituted with at least one acid functional group, a heteroaryl substituted with at least one acid functional group, a monosaccharide substituted with at least one acid functional group and an oligosaccharide substituted with at least one acid functional group, wherein the at least one acid functional group substituted on R₁ is selected from the group consisting of —CO₂H; —SO₃H; —SO₂H; —PO₃H₂; —OSO₃H; -alkyl-CO₂H; -alkyl-SO₃H; -alkyl-SO₂H; -alkyl-PO₃H₂ and -alkyl-OSO₃H and wherein the alkyl group is a C₁–C₄ alkyl group.
 2. The compound defined in claim 1, wherein X₁ is hydrogen and X₂ is an electronegative atom or an electronegative group.
 3. The compound defined in claim 1, wherein X₂ is hydrogen and X₁ is an electronegative atom or an electronegative group.
 4. The compound defined in claim 1, wherein one of X₁ and X₂ is hydrogen and the other of X₁ and X₂ is —NO₂.
 5. A pharmaceutical composition comprising the compound defined in claim 1, together with a pharmaceutically acceptable carrier.
 6. The compound defined in claim 1, wherein the compound of Formula 3 is 3-nitro-N-(p-carboxyphenyl)-1,8-naphthalimide or a pharmaceutically acceptable salt thereof.
 7. A pharmaceutical composition comprising the compound defined in claim 6, together with a pharmaceutically acceptable carrier.
 8. The compound defined in claim 1, wherein the compound of Formula 3 is 3-nitro-N-(m-carboxyphenyl)-1,8-naphthalimide or a pharmaceutically acceptable salt thereof.
 9. A pharmaceutical composition comprising the compound defined in claim 8, together with a pharmaceutically acceptable carrier.
 10. The compound defined in claim 1, wherein the compound of Formula 3 is 3-nitro-N-(o-carboxyphenyl)-1,8-naphthalimide or a pharmaceutically acceptable salt thereof.
 11. A pharmaceutical composition comprising the compound defined in claim 10, together with a pharmaceutically acceptable carrier.
 12. The compound defined in claim 1, wherein the compound of Formula 3 is 3-nitro-N-(p-carboxyphenylmethyl)-1,8-naphthalimide or a pharmaceutically acceptable salt thereof.
 13. A pharmaceutical composition comprising the compound defined in claim 12, together with a pharmaceutically acceptable carrier.
 14. The compound defined in claim 1, wherein the compound of Formula 3 is 4-nitro-N-(p-carboxyphenyl)-1,8-naphthalimide or a pharmaceutically acceptable unit thereof.
 15. A pharmaceutical composition comprising the compound defined in claim 14, together with a pharmaceutically acceptable carrier.
 16. The compound defined in claim 1, wherein the compound of Formula 3 is 4-nitro-N-(m-carboxyphenyl)-1,8-naphthalimide or a pharmaceutically acceptable salt thereof.
 17. A pharmaceutical composition comprising the compound defined in claim 16, together with a pharmaceutically acceptable carrier.
 18. The compound defined in claim 1, wherein the compound of Formula 3 is 4-nitro-N-(o-carboxyphenyl)-1,8-naphthalimide or a pharmaceutically acceptable salt thereof.
 19. A pharmaceutical composition comprising the compound defined in claim 18, together with a pharmaceutically acceptable carrier. 